[Profile] Fix gcov tests

Summary: The gcda need to be delete before running the binary to avoid to have an increasing "# of Runs" when a test is failing

Reviewers: vitalybuka, eugenis, marco-c

Reviewed By: marco-c

Subscribers: delcypher, llvm-commits, #sanitizers, sylvestre.ledru, marco-c

Differential Revision: https://reviews.llvm.org/D52456

llvm-svn: 342963